A 851, by itself an autonomous extrageneric fragment or pensée, is also a variant version of a rough-copy fragment (A 879) composed in the last decade of Dickinson's life. In this case the closing passage of the text inscribed on A 851—"A something | overtakes the | Mind -"—appears, slightly altered, as the concluding passage of the text inscribed on A 879, "A something | over takes the | mind - we do | not hear it | coming." The precise nature of the relationship between the two fragments, one a meditation on the disorienting experience of reading poetry, the other on the similarly disorienting experience of reading (the book of) nature, remains unknown. Neither fragment was incorporated into another extant composition.